Truncal fat in relation to total body fat: influences of age, sex, ethnicity and fatness

Objective: To investigate the influence of age, sex, ethnicity and total fatness on central obesity in four ethnic populations. Design: Cross-sectional analysis of study subjects enrolled from 1993 to 2005. Subjects: A multi-ethnic (Caucasian (CA), African-American (AA), Hispanic-American (HA) and Asian (As)) convenience sample of 604 men and 1192 women (aged 18-96 years, body mass index 15.93-45.80 kg/m2). Measurements: Total body fat (TBF) and truncal fat were measured by dual-energy X-ray absorptiometry. General linear regression models were used to test for independent associations with log10-transformed truncal fat. Results: For all ethnicities, men had a lower percent body fat and more truncal fat than women. Log10-transformed truncal fat increased with TBF approximately as a square root function. At older ages, there was a greater amount of truncal fat in CA, HA and As men (approximately 0.20-0.25 kg/decade) with the effect more pronounced in AA men (approximately 0.33 kg/decade). For women, the increment of truncal fat per decade was reduced in CA and AA women (approximately 0.07 kg) compared with As and HA women (approximately 0.33 kg). Adjusted for mean values of covariates in our sample, AA had less truncal fat than As. Conclusion: The accumulation of truncal fat is strongly related to age, ethnicity and total fatness in both men and women.